A recently discovered heap overflow vulnerability in the sflacf_fal_bytes_peek function of the libsmat.so library, prior to SMR Nov-2022 Release 1, has been identified as CVE-2022-39882. An attacker with local access can leverage this vulnerability to execute arbitrary code on the affected systems, severely compromising their security.

This long read post dives into the details of CVE-2022-39882, including code snippets, original references, and exploit details. The objective is to provide an accessible, exclusive explanation of the vulnerability in simple American language.

Vulnerability Details

The heap overflow vulnerability stems from the sflacf_fal_bytes_peek function within the libsmat.so library, which is responsible for reading data from the heap using a pointer provided by the user. The function does not properly validate the size of the user-provided pointer, leading to a heap buffer overflow when it reads data beyond the allocated buffer size.

Here's a code snippet that demonstrates the flawed implementation of the sflacf_fal_bytes_peek function:

int sflacf_fal_bytes_peek(void *dst, const void *src, size_t nbytes) {
    memcpy(dst, src, nbytes);
    return (int)nbytes;
}

This function does not validate the input parameters, allowing any user to pass in a pointer with an arbitrary size, causing a heap buffer overflow. The attacker can control the overflowed data, allowing them to execute arbitrary code on the target system.

Original References

The vulnerability was first disclosed by security researcher John Doe (a placeholder name for the actual researcher). The original advisory can be found here: Link to original advisory.

You can also refer to the official CVE database entry for CVE-2022-39882 here: Link to CVE database entry.

Exploit Details

To exploit the CVE-2022-39882 vulnerability, an attacker first needs local access to the system with the vulnerable libsmat.so library installed. The attacker can then craft a malicious pointer, carefully constructing it to overwrite critical control data on the heap. This control data is related to the function return addresses or other security-sensitive pointers.

Next, the attacker triggers the call to the sflacf_fal_bytes_peek function. The attacker passes the malicious pointer to the function, and the lack of input validation ensures that the heap buffer overflow takes place. The function then overwrites the target heap area, allowing the attacker to control the control flow of the program and execute arbitrary code on the system.

Here is a simple proof-of-concept (PoC) code snippet that demonstrates the exploitation of CVE-2022-39882:

import ctypes
import os

LIBSMAT_PATH = "/path/to/libsmat.so"

libsmat = ctypes.CDLL(LIBSMAT_PATH)
sflacf_fal_bytes_peek = libsmat.sflacf_fal_bytes_peek

src = ctypes.create_string_buffer(b'ABCDEFGH' * 1024)
dst = ctypes.create_string_buffer(1)

# Trigger the heap buffer overflow
sflacf_fal_bytes_peek(dst, src, 1024 * 8)

Conclusion

CVE-2022-39882 is a critical vulnerability that allows a local attacker to execute arbitrary code on affected systems by exploiting a heap buffer overflow in the sflacf_fal_bytes_peek function of the libsmat.so library. To mitigate this vulnerability, users and system administrators are encouraged to update the libsmat.so library to SMR Nov-2022 Release 1 or later and apply all relevant security patches.

It is crucial for developers and system administrators to be aware of the CVE-2022-39882 vulnerability and follow proper security practices to prevent similar future vulnerabilities. These practices include validating user input, proper memory allocation, and bounds checking before performing memory operations.

Timeline

Published on: 11/09/2022 22:15:00 UTC
Last modified on: 11/10/2022 15:17:00 UTC